1. Field of the Invention
The present invention relates to a method for a reactive surface treatment of a workpiece, according to which a treatment gas is led out of at least one infeed opening into a treatment chamber, is drawn off from said treatment chamber through at least one draw off opening, which openings are arranged adjacent of each other over and across the area of the surface to be treated and feature axes of the openings which extend at least approximately perpendicularly to the surface to be treated.
The invention relates further to a treatment chamber for a reactive surface treatment of a workpiece, including a support for a positioning of the surface of the workpiece to be treated in the chamber, and oppositely of the positioned surface at least one infeed opening for a treatment gas connected to a gas delivery device, at least one gas draw off opening for gas connected to a gas draw off device in which at least one gas draw off opening is located directly adjacent the infeed openings and whereby the axes of the opening(s) extend at least approximately perpendicularly to the area of the surface located oppositely of the openings.
The present invention relates basically to the forming of the gas flow at reactive surface treatment processes, i.e. the delivering or feeding, respectively of a treatment gas having gas components which react chemically during the surface treatment and the drawing off of gas from the treatment chamber as well, which gas includes the reaction products of the above mentioned reaction.
2. Description of the Prior Art
The French specification FR-A-26 23 524 discloses a CVD-coating method according to which the treatment gas is fed into the chamber laterally at the side of the surface to be treated and the gas including the product of the reaction is led off through a plurality of draw off openings located oppositely of the surface.
The European specification EP-A-O 283 007 discloses a CVD-coating method according to which the treatment gas is fed into the chamber from a plurality of openings located opposite of the surface to be coated and the gas including the products of the reaction is drawn off laterally at the side of the surface to be treated.
The European specification EP-A-O 322 466 discloses a plasma supported (PE-) CVD-method according to which the treatment gas is led in from a plurality of openings located oppositely of the surface to be treated and the products of the reaction are led off through a draw off opening which is located relative to the workpiece substantially opposite of the inlet openings such that the gas flow proceeds radially around the periphery of the workpiece towards the draw off opening.
The European specification EP-A-O 303 508 discloses in turn a PECVD-method according to which the treatment gas, whereby the work piece is arranged in its treatment position, is fed out of a plurality of openings located opposite of the surface to be treated, and whereby gas with the products of the reaction is drawn off laterally at the side of the surface to be treated.
In the framework of CVD-methods conducted under atmospheric and vacuum conditions as well, the U.S. Pat. No. 4,817,558 patent document discloses a feeding of treatment gas from openings located opposite of the surface to be treated and again to draw off the products of the reaction laterally or peripherically, resp. of the surface to be treated.
At the other hand, the European specification EP-A-0 254 654 discloses to lead the gas flow substantially over and across the entire surface to be treated, i.e. to feed the treatment gas at the one side of the surface to be treated thereagainst and to draw it again off at the other side.
Finally, the U.S. Pat. No. 4,297,162 patent document discloses to feed the treatment gas used in an RF-plasma-etching method from a plurality of openings to the surface to be treated located opposite of the surface, whereby the openings are located at different distances relative to the surface to be treated such to arrive at a desired etching profile at the surface of the workpiece. The gas and accordingly the products of the reaction of the reactive etching process are drawn out of the chamber by a vacuum pump connected to the chamber. The draw off conduit is located relative to the workpiece to be treated at the side opposite the infeed openings, such that the gas flow proceeds radially around the periphery of the workpiece to the draw off opening located centrally below the workpiece.
In reactive surface treatment processes in which at least a portion of the treatment gas reacts chemically, the relationship between the concentration of reaction gas which has not yet been consumed and the gaseous reaction products in the direct vicinity of the surface to be treated is to be given careful attention regarding the effect of the treatment, i.e. rate of coating or etching, resp. the term "rate" is here to be understood as: amount per unit of time.
If a flow of freshly fed reactive treatment gas wafts over the surface and reacts the above-mentioned relationship is continuously changed in the flow to the disadvantage of the fresh reactive gas such that also the effect of the treatment changes along the surface over which the gas wafts. The above-mentioned known procedures do not take this phenomenon into account. This phenomenon occurs always when a gas flow wafts over a large area substantially continuously over the surface to be treated. This, accordingly in such a case if treatment gas is fed from a plurality of gas inlets to the surface to be treated and relative thereto gas with reaction products is peripherically drawn off: In such case an extensive gas flow is produced which is directed radially or from the centre to the periphery.
Now, the U.S. Pat. No. 4,209,357 discloses to foresee in the framework of a plasma etching method a plurality of infeed openings for the treatment gas and a plurality of draw off openings as well opposite of the surface of the workpiece which openings allow together a uniform feeding of treatment gas and drawing off of gas in the reaction chamber.
The German specification DE-OS-30 20 815 discloses a plasma supported reactive coating process in which the treatment gas is fed from a supply chamber through openings in one of the glow discharge electrodes into the treatment chamber proper between the electrodes and to lead the reaction products through the same openings out of the treatment chamber into the same supply chamber whereby the flow of the treatment gas to and into the treatment chamber and of the reaction products from and out of the treatment chamber back into the supply chamber proceeds based on a gas diffusion.
In this procedure the distribution of the treatment gas and of the reaction products can hardly be controlled in the treatment chamber. Thus, it is not guaranteed that fresh reaction gas is present at the area of the workpiece to be coated in a predominant measure because such depends decisively at the one hand from the distribution of the reaction in the treatment chamber and of the speeds of the diffusion of the fresh treatment gas as well, and at the other hand from the reaction products.